To my surprise doesn't seem to have generated much discussion on here, at least based on some quick searches.
The latest edition of The National Fire Protection Association Journal has a piece looking at this "national crusade" and growing interest in "point-access blocks".
"calls on architects, designers, and urban planners...to reimagine the potential of...mid-rise buildings, up to six stories high, on underutilized lots in Denver."
I know both in the last Denver mayoral race and in last CO legislative cycle this issue seemed to be getting some traction but nothing (yet) has come of those discussions AFAIK. Maybe the competition can help drive a new wave of policy/PR locally.
Or rather, I completely agree with the intent and thinking behind the "single stair movement" but I don't believe that 1) it is a major cause of the housing shortage/ high prices (but probably a contributing factor and 2) that this would be used for anything other than increasing profit margins on the standard 4 over 1 podium stick frame apartment building in the middle of a parking lot in the suburbs with a minimum 1.5:1 parking ratio that is a 20 minute walk from the shittiest bus line a European ever imagined.
Yup. Because doing a via ferrata 80 feet up at 3 am in January while your code minimum plywood building is on fire is something anyone can easily do. ;)
IBC multiple stair requirements do have a disproportionately large negative effect on high-rise residential projects. There is no data to back up the requirement: where Type 1 construction and fully sprinklered high-rise buildings adhere to basic travel distance requirements per floor, the risk to residents in a fire is very, very low.
A good step towards fixing the code would be to allow scissor stairs again (two stairs contained within a single enclosure). This is fairly common in some local markets (Vancouver, BC), and there have never been any problems with them.
One of the bigger issues, more generally, with the International model codes is that they are always the worst possible combination of belt-and-suspenders over-design and bolting-the-door-after-the-horse-has-escaped over-reaction.
I can see that on hi-rise buildings. Then again, look at the WTC and the egress time with three stair towers.
Are you encountering a lot of Type 1 construction for mid-rise buildings?
Oct 14, 24 1:29 pm ·
·
gwharton
Mid-rise is all Type III and Type V-A podium stuff, and the plates are big enough that exit distance considerations would override other factors. So most of them would still have to have at least two exits, and that wouldn't really have a big impact on plate efficiency (assuming a double-loaded corridor). It's a much bigger deal for tower design. The Seattle Building Code allows single-stair buildings up to 4 stories with sprinklers, etc., and also waives a bunch of the IBC high rise stuff (like enclosed elevator lobbies) for buildings which meet other safety requirements. Seattle has always had major differences with the UBC/IBC related to things like this.
As for the WTC collapse, even twice as many exits as there were wouldn't have saved any more lives. The buildings came down too fast and the damage was too extreme for that to have really made much difference.
I agree about the WTC. I'm not saying more stairs would save more lives. Sorry for the confusion. I was saying look at the exiting times as a data point. I think it's one of the few that we have in the US.
I also agree about the exiting in the mid-rise buildings. In Colorado I see a lot of podium budlings with four story V-b over a one story II-b.
Oct 14, 24 1:41 pm ·
·
gwharton
Number of exits as a life-safety / exit time factor is more closely related to plate size and exit access travel distance, and the safe distance increases with other factors such as non-combustible construction and sprinklers. The codes already account for all that, fairly reasonably imo. What the codes don't account for is that there is a lower threshold on plate size below which it doesn't really make sense to require more than one exit. Yet the code requires two as a baseline in nearly all cases down to the smallest floor plates. That's the part which needs to be fixed. Scissor stairs, which I mentioned above, are a good option as well: allowing multiple exit access points on a floor for reduced travel times without requiring large volumes inside the building envelope for completely separate stair enclosures. They can even be designed so that each exit within the scissor stair enclosure is 100% smoke-isolated from the other.
As an example for high-rise residential buildings, Seattle House, a 440-foot two-tower condominium project currently under construction in downtown Seattle on which I was both Managing Principal and did a lot of design and planning work, is highly restricted in the plate sizes of each tower due to Seattle tower spacing requirements from the zoning code (another project was permitted across the alley before it, though it's not built yet). Each of the two towers has a floor plate size of around 7,000 sq. ft. (which is very small for a Seattle condo tower).
Each tower needs two stairways, with required separation distance between the exit access doors. Structural core requirements for a 44-story building also take a big bite out of the plan. Even with a fairly efficient and compact plan, the second stair reduced net rentable area per floor by 3.3%. Now, that may not seem like a lot, but in this building that resulted in a loss of around 21,000 sq. ft. total, or three entire floors of one tower. Where if we had been able to do scissor stairs, we could have built 28 more units at only minor additional cost.
You'll get no argument from me on this. I totally understand. In the medical and education sectors, small increases to circulation can severely reduce exam room / classroom area.
Before anyone say so - simply moving a stair to an outside wall / corner doesn't solve this issue and often creates other issues.
Fun fact: The first NBBJ Amazon office tower across the way has unitized curtainwall with single hung operable windows. Not sure if this "feature" was utilized for the subsequent towers.
Oct 14, 24 3:48 pm ·
·
gwharton
Seattle House, like most residential towers in Seattle, uses a window wall system rather than a curtain wall. It's a fair bit cheaper, and a whole lot easier to install with residential tower sequencing.
Oct 14, 24 5:00 pm ·
·
t a z
Apologies, my comment was more about the novelty of providing office workers in a tower with individually operable windows that aren't controlled / operated by a BMS - I always wondered how that turned out, i.e. does housekeeping check to make sure all the windows are closed at the end of the day?
BMS, invented to be used by property owners/land lords to have more control over their tenants comfort or discomfort. The secret truth hidden behind the veil of some "other purpose" to distract you from their real purpose and agenda. Oh wait, that's exposing their "dark side" or maybe we just don't want to know and purge the image that comes to mind of their 'dark side'.
When you have high occupancy count.... a high rise residential MFR is basically going to have occupancy quantities equal to that of assembly use and you need multiple stairs. Going out windows just is not a viable option unless suicide and reducing the human population is your answer to that. A single stair in an SFR or a duplex might be fine. However, you would expect to need something along the lines of more than 1 stairs because you are talking redundancy in means of egress in case one stairs is cut off by a fire. You got to think of worst case scenario of a high rise MFR with a ranging fire inside and say was caused by several concurrent fires from different units going out of control and is like a literal nightmare story. How do you design to save the most lives? That is the driving force of such. We are talking fires like a city is on fire and is like the plot of a disaster movie. How do you design for that situation.
We designed a small 6plex infill project in an established Neighbourhood. The lot was small. The two stairs we had to design certainly took a lot out of the living spaces. This is a design that could have used a single stair for exit and I don't think life safety would have been effected. The plan looks a little crazy with the 2 stairs eating up all the space on the lot.
Can't use spiral stairs? Haven't looked specifically in the current edition codes if spiral stairs be used in R-1/R-2 occupancies.
Oct 15, 24 5:57 pm ·
·
Almosthip
Have you ever moved furniture up spiral stairs? Can not do spiral stairs here in Alberta for multifamily residential buildings. No fire escapes either.
Yeah, good point there. If you want to move furniture, F--- stairs... put an elevator! Some furniture, leave on ground floor level(s). On the occasion, you might have to ground levels that can access multiple floor levels. Depends on terrain topography for that and occasionally a little bit of "engineering". Otherwise it would usually be one maybe two floor levels that can be accessed. Three stories accessible without needing interior or attached exterior staircase is more rarer. Usually terrain is flat or might have a little bit of terrain profile that allows accessing at two levels without such stairs and can be accessed by ramping the terrain a little as needed and such. This probably not the case for your 6-plex.
We can use scissor stairs in Canada, though they have to be rated between them. We've done two of them so far and mostly it saves the cost of one of the walls (full height of building) but then you've got to fire seal all the joints, but it is a cost and SF savings, if you can do it. It really only works with small footprint buildings because there's a max 6m/20' dead end corridor clause, which effectively becomes half (or maybe a third) the length of the corridor
gwharton I'm in nearly the exact position in a few projects. What exactly are you basing your argument on with building officials'? Thanks
Oct 16, 24 6:56 pm ·
·
gwharton
Ultimately, we have to do what the local building code requires. In Seattle, 4 stories and under, that means we can do one stair so long as the plate size and exit access travel distance meet the requirements. Otherwise, we have to add the second stair. Fortunately, even in high-rise projects, Seattle does not generally require a THIRD stair as is sometimes necessary in high-rises in the plain-vanilla IBC.
The single stair idea seemed reasonable to me, and is pretty normal in Japan. But then we saw the Grenfell fire and the fallout from that debacle. It seems like that building was messed up on so many levels that it may not be representative, but I cant help but see it as the inevitable result of rules that favor development goals over safety. Not that single set of stairs cannot work, but tradeoffs need to be less dumb.
The way we get around the issue in Japan is that balconies (which dont count in FAR ratios) have collapsible ladders embedded in them, and turn every facade into an external second egress in an emergency. Continuous balconies also have punch-out panels in the dividing screens between units, meaning you can exit through your neighbor's unit in a pinch as well. This works well with mid-rise buildings, which is what most of Tokyo is composed of. It's cheap-ish, simple, flexible, and easy to work with because the code supports it in other ways (see above, balconies don't count in FAR calcs). I've seen similar examples in other parts of the world, so it is not like there are not enough examples and counter-examples to make a decent policy and/or laws.
North America feels a lot less rational than other countries I have worked in. But the current housing crisis is likely to be the source for a lot of rethink on building code. This one seems to be of the low-hanging fruit variety, as long as it is done with a modicum of care.
I went to a presentation by Utile in Boston recently. They have a research project that proposes legalizing single stairs in Massachusetts with specific requirements that address a lot of the issues that are raised in this thread.
I think it is well worth looking at, particularly in areas where we want to encourage denser infill--which should be all cities.
The "single-stair" movement
To my surprise doesn't seem to have generated much discussion on here, at least based on some quick searches.
The latest edition of The National Fire Protection Association Journal has a piece looking at this "national crusade" and growing interest in "point-access blocks".
Any 'Nectors attend the relevant session at AIA24? Or the recent nfpa.org/singleexitsymposium?
On a related note, The Denver Single-Stair Housing Challenge
"calls on architects, designers, and urban planners...to reimagine the potential of...mid-rise buildings, up to six stories high,
on underutilized lots in Denver."
I know both in the last Denver mayoral race and in last CO legislative
cycle this issue seemed to be getting some traction but nothing (yet) has come of those discussions AFAIK. Maybe the competition can help drive a new wave of policy/PR locally.
I'm extremely skeptical.
Or rather, I completely agree with the intent and thinking behind the "single stair movement" but I don't believe that 1) it is a major cause of the housing shortage/ high prices (but probably a contributing factor and 2) that this would be used for anything other than increasing profit margins on the standard 4 over 1 podium stick frame apartment building in the middle of a parking lot in the suburbs with a minimum 1.5:1 parking ratio that is a 20 minute walk from the shittiest bus line a European ever imagined.
Completely right - in NYC
.
Yup. Because doing a via ferrata 80 feet up at 3 am in January while your code minimum plywood building is on fire is something anyone can easily do. ;)
Do you even Aussie Rappel bro?
I do bro! I also simul rap bro! ;)
IBC multiple stair requirements do have a disproportionately large negative effect on high-rise residential projects. There is no data to back up the requirement: where Type 1 construction and fully sprinklered high-rise buildings adhere to basic travel distance requirements per floor, the risk to residents in a fire is very, very low.
A good step towards fixing the code would be to allow scissor stairs again (two stairs contained within a single enclosure). This is fairly common in some local markets (Vancouver, BC), and there have never been any problems with them.
One of the bigger issues, more generally, with the International model codes is that they are always the worst possible combination of belt-and-suspenders over-design and bolting-the-door-after-the-horse-has-escaped over-reaction.
I can see that on hi-rise buildings. Then again, look at the WTC and the egress time with three stair towers.
Are you encountering a lot of Type 1 construction for mid-rise buildings?
Mid-rise is all Type III and Type V-A podium stuff, and the plates are big enough that exit distance considerations would override other factors. So most of them would still have to have at least two exits, and that wouldn't really have a big impact on plate efficiency (assuming a double-loaded corridor). It's a much bigger deal for tower design. The Seattle Building Code allows single-stair buildings up to 4 stories with sprinklers, etc., and also waives a bunch of the IBC high rise stuff (like enclosed elevator lobbies) for buildings which meet other safety requirements. Seattle has always had major differences with the UBC/IBC related to things like this.
As for the WTC collapse, even twice as many exits as there were wouldn't have saved any more lives. The buildings came down too fast and the damage was too extreme for that to have really made much difference.
Thanks for the info!
I agree about the WTC. I'm not saying more stairs would save more lives. Sorry for the confusion. I was saying look at the exiting times as a data point. I think it's one of the few that we have in the US.
I also agree about the exiting in the mid-rise buildings. In Colorado I see a lot of podium budlings with four story V-b over a one story II-b.
Number of exits as a life-safety / exit time factor is more closely related to plate size and exit access travel distance, and the safe distance increases with other factors such as non-combustible construction and sprinklers. The codes already account for all that, fairly reasonably imo. What the codes don't account for is that there is a lower threshold on plate size below which it doesn't really make sense to require more than one exit. Yet the code requires two as a baseline in nearly all cases down to the smallest floor plates. That's the part which needs to be fixed. Scissor stairs, which I mentioned above, are a good option as well: allowing multiple exit access points on a floor for reduced travel times without requiring large volumes inside the building envelope for completely separate stair enclosures. They can even be designed so that each exit within the scissor stair enclosure is 100% smoke-isolated from the other.
I completely agree gwharton.
As an example for high-rise residential buildings, Seattle House, a 440-foot two-tower condominium project currently under construction in downtown Seattle on which I was both Managing Principal and did a lot of design and planning work, is highly restricted in the plate sizes of each tower due to Seattle tower spacing requirements from the zoning code (another project was permitted across the alley before it, though it's not built yet). Each of the two towers has a floor plate size of around 7,000 sq. ft. (which is very small for a Seattle condo tower).
Each tower needs two stairways, with required separation distance between the exit access doors. Structural core requirements for a 44-story building also take a big bite out of the plan. Even with a fairly efficient and compact plan, the second stair reduced net rentable area per floor by 3.3%. Now, that may not seem like a lot, but in this building that resulted in a loss of around 21,000 sq. ft. total, or three entire floors of one tower. Where if we had been able to do scissor stairs, we could have built 28 more units at only minor additional cost.
You'll get no argument from me on this. I totally understand. In the medical and education sectors, small increases to circulation can severely reduce exam room / classroom area.
Before anyone say so - simply moving a stair to an outside wall / corner doesn't solve this issue and often creates other issues.
Fun fact: The first NBBJ Amazon office tower across the way has unitized curtainwall with single hung operable windows. Not sure if this "feature" was utilized for the subsequent towers.
Seattle House, like most residential towers in Seattle, uses a window wall system rather than a curtain wall. It's a fair bit cheaper, and a whole lot easier to install with residential tower sequencing.
Apologies, my comment was more about the novelty of providing office workers in a tower with individually operable windows that aren't controlled / operated by a BMS - I always wondered how that turned out, i.e. does housekeeping check to make sure all the windows are closed at the end of the day?
BMS, invented to be used by property owners/land lords to have more control over their tenants comfort or discomfort. The secret truth hidden behind the veil of some "other purpose" to distract you from their real purpose and agenda. Oh wait, that's exposing their "dark side" or maybe we just don't want to know and purge the image that comes to mind of their 'dark side'.
.
When you have high occupancy count.... a high rise residential MFR is basically going to have occupancy quantities equal to that of assembly use and you need multiple stairs. Going out windows just is not a viable option unless suicide and reducing the human population is your answer to that. A single stair in an SFR or a duplex might be fine. However, you would expect to need something along the lines of more than 1 stairs because you are talking redundancy in means of egress in case one stairs is cut off by a fire. You got to think of worst case scenario of a high rise MFR with a ranging fire inside and say was caused by several concurrent fires from different units going out of control and is like a literal nightmare story. How do you design to save the most lives? That is the driving force of such. We are talking fires like a city is on fire and is like the plot of a disaster movie. How do you design for that situation.
How will one stair be enough?
Sprinkler systems throughout.
Everything is concrete.... even the bed.lol
We designed a small 6plex infill project in an established Neighbourhood. The lot was small. The two stairs we had to design certainly took a lot out of the living spaces. This is a design that could have used a single stair for exit and I don't think life safety would have been effected. The plan looks a little crazy with the 2 stairs eating up all the space on the lot.
Can't use spiral stairs? Haven't looked specifically in the current edition codes if spiral stairs be used in R-1/R-2 occupancies.
Have you ever moved furniture up spiral stairs? Can not do spiral stairs here in Alberta for multifamily residential buildings. No fire escapes either.
Yeah, good point there. If you want to move furniture, F--- stairs... put an elevator! Some furniture, leave on ground floor level(s). On the occasion, you might have to ground levels that can access multiple floor levels. Depends on terrain topography for that and occasionally a little bit of "engineering". Otherwise it would usually be one maybe two floor levels that can be accessed. Three stories accessible without needing interior or attached exterior staircase is more rarer. Usually terrain is flat or might have a little bit of terrain profile that allows accessing at two levels without such stairs and can be accessed by ramping the terrain a little as needed and such. This probably not the case for your 6-plex.
We can use scissor stairs in Canada, though they have to be rated between them. We've done two of them so far and mostly it saves the cost of one of the walls (full height of building) but then you've got to fire seal all the joints, but it is a cost and SF savings, if you can do it. It really only works with small footprint buildings because there's a max 6m/20' dead end corridor clause, which effectively becomes half (or maybe a third) the length of the corridor
Are ya sure cause in Alberta our 2 stairs are not allowed to share a common wall.
I think it's just a Vancouver or BC thing? Maybe it's okay in Toronno as well?
Almosthip can you point to the code item that says so? Could be a provincial amendment?
gwharton
I'm in nearly the exact position in a few projects. What exactly are you basing your argument on with building officials'? Thanks
Ultimately, we have to do what the local building code requires. In Seattle, 4 stories and under, that means we can do one stair so long as the plate size and exit access travel distance meet the requirements. Otherwise, we have to add the second stair. Fortunately, even in high-rise projects, Seattle does not generally require a THIRD stair as is sometimes necessary in high-rises in the plain-vanilla IBC.
The single stair idea seemed reasonable to me, and is pretty normal in Japan. But then we saw the Grenfell fire and the fallout from that debacle. It seems like that building was messed up on so many levels that it may not be representative, but I cant help but see it as the inevitable result of rules that favor development goals over safety. Not that single set of stairs cannot work, but tradeoffs need to be less dumb.
The way we get around the issue in Japan is that balconies (which dont count in FAR ratios) have collapsible ladders embedded in them, and turn every facade into an external second egress in an emergency. Continuous balconies also have punch-out panels in the dividing screens between units, meaning you can exit through your neighbor's unit in a pinch as well. This works well with mid-rise buildings, which is what most of Tokyo is composed of. It's cheap-ish, simple, flexible, and easy to work with because the code supports it in other ways (see above, balconies don't count in FAR calcs). I've seen similar examples in other parts of the world, so it is not like there are not enough examples and counter-examples to make a decent policy and/or laws.
North America feels a lot less rational than other countries I have worked in. But the current housing crisis is likely to be the source for a lot of rethink on building code. This one seems to be of the low-hanging fruit variety, as long as it is done with a modicum of care.
I went to a presentation by Utile in Boston recently. They have a research project that proposes legalizing single stairs in Massachusetts with specific requirements that address a lot of the issues that are raised in this thread.
I think it is well worth looking at, particularly in areas where we want to encourage denser infill--which should be all cities.
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